Regarding things never being the same again, I agree. And not just the one who has been cheated on. The cheater changes - from the very first occasion.
A long time ago, there was a series by John D. MacDonald about a character named Travis McGee. McGee fell in love quite often, but one woman at a time, according to the story line. But in one novel, circumstances caused the woman in his life at that time to feel that the trust had been broken.
Travis was heartbroken, but he discovered that even though things were nominally "worked out," the trust would never be the same again.
I discovered that for myself after the breakup of my first marriage, and I was heartbroken for a long time. Years. And I still have some sorrow, and that was in 1985.
Thankfully, though, I became a better person. And my ex became happier, also. And, at the right time, I met the woman who is everything to me.
Not only would I not want to damage my own heart, or cheapen our relationship, or abuse our trust, or hurt Marge, the simple fact of the matter is that Marge keeps me so happy that I would not want to even appear to be thinking of being unfaithful.
I am a lucky man.